4 research outputs found
Appreciating the First Line of the Human Innate Immune Defense: A Strategy to Model and Alleviate the Neutrophil Elastase-Mediated Attack toward Bioactivated Biomaterials
Biointerface engineering is a wide-spread strategy to improve the healing process and subsequent tissue integration of biomaterials. Especially the integration of specific peptides is one promising strategy to promote the regenerative capacity of implants and 3D scaffolds. In vivo, these tailored interfaces are, however, first confronted with the innate immune response. Neutrophils are cells with pronounced proteolytic potential and the first recruited immune cells at the implant site; nonetheless, they have so far been underappreciated in the design of biomaterial interfaces. Herein, an in vitro approach is introduced to model and analyze the neutrophil interaction with bioactivated materials at the example of nano-bioinspired electrospun surfaces that reveals the vulnerability of a given biointerface design to the contact with neutrophils. A sacrificial, transient hydrogel coating that demonstrates optimal protection for peptide-modified surfaces and thus alleviates the immediate cleavage by neutrophil elastase is further introduced
A Biomimetic, Copolymeric Membrane for CellâStretch Experiments with Pulmonary Epithelial Cells at the AirâLiquid Interface
Chronic respiratory diseases are among the leading causes of death worldwide, but only symptomatic therapies are available for terminal illness. This in part reflects a lack of biomimetic in vitro models that can imitate the complex environment and physiology of the lung. Here, a copolymeric membrane consisting of poly(Δâ)caprolactone and gelatin with tunable properties, resembling the main characteristics of the alveolar basement membrane is introduced. The thin bioinspired membrane (â€5 ÎŒm) is stretchable (up to 25% linear strain) with appropriate surface wettability and porosity for culturing lung epithelial cells under airâliquid interface conditions. The unique biphasic concept of this membrane provides optimum characteristics for initial cell growth (phase I) and then switch to biomimetic properties for cyclic cellâstretch experiments (phase II). It is showed that physiologic cyclic mechanical stretch improves formation of Fâactin cytoskeleton filaments and tight junctions while nonâphysiologic overâstretch induces cell apoptosis, activates inflammatory response (ILâ8), and impairs epithelial barrier integrity. It is also demonstrated that cyclic physiologic stretch can enhance the cellular uptake of nanoparticles. Since this membrane offers considerable advantages over currently used membranes, it may lead the way to more biomimetic in vitro models of the lung for translation of in vitro response studies into clinical outcome
Three-Dimensional Polydopamine Functionalized Coiled Microfibrous Scaffolds Enhance Human Mesenchymal Stem Cells Colonization and Mild Myofibroblastic Differentiation
Electrospinning has been widely applied
for tissue engineering due to its versatility of fabricating extracellular
matrix (ECM) mimicking fibrillar scaffolds. Yet there are still challenges
such as that these two-dimensional (2D) tightly packed, hydrophobic
fibers often hinder cell infiltration and cellâscaffold integration.
In this study, polycaprolactone (PCL) was electrospun into a grounded
coagulation bath collector, resulting in 3D coiled microfibers with <i>in situ</i> surface functionalization with hydrophilic, catecholic
polydopamine (pDA). The 3D scaffolds showed biocompatibility and were
well-integrated with human bone marrow derived human mesenchymal stem
cells (hMSCs), with significantly higher cell penetration depth compared
to that of the 2D PCL microfibers from traditional electrospinning.
Further differentiation of human mesenchymal stem cells (hMSCs) into
fibroblast phenotype <i>in vitro</i> indicates that, compared
to the stiff, tightly packed, 2D scaffolds which aggravated myofibroblasts
related activities, such as upregulated gene and protein expression
of α-smooth muscle actin (α-SMA), 3D scaffolds induced
milder myofibroblastic differentiation. The flexible 3D fibers further
allowed contraction with the well-integrated, mechanically active
myofibroblasts, monitored under live-cell imaging, whereas the stiff
2D scaffolds restricted that
A Bioinspired in vitro Lung Model to Study Particokinetics of Nano-/Microparticles Under Cyclic Stretch and Air-Liquid Interface Conditions
Evolution has endowed the lung with exceptional design providing a large surface area for gas exchange area (ca. 100 m) in a relatively small tissue volume (ca. 6 L). This is possible due to a complex tissue architecture that has resulted in one of the most challenging organs to be recreated in the lab. The need for realistic and robust in vitro lung models becomes even more evident as causal therapies, especially for chronic respiratory diseases, are lacking. Here, we describe the Cyclic In VItro Cell-stretch (CIVIC) âbreathingâ lung bioreactor for pulmonary epithelial cells at the air-liquid interface (ALI) experiencing cyclic stretch while monitoring stretch-related parameters (amplitude, frequency, and membrane elastic modulus) under real-time conditions. The previously described biomimetic copolymeric BETA membrane (5 ÎŒm thick, bioactive, porous, and elastic) was attempted to be improved for even more biomimetic permeability, elasticity (elastic modulus and stretchability), and bioactivity by changing its chemical composition. This biphasic membrane supports both the initial formation of a tight monolayer of pulmonary epithelial cells (A549 and 16HBE14o) under submerged conditions and the subsequent cell-stretch experiments at the ALI without preconditioning of the membrane. The newly manufactured versions of the BETA membrane did not improve the characteristics of the previously determined optimum BETA membrane (9.35% PCL and 6.34% gelatin [w/v solvent]). Hence, the optimum BETA membrane was used to investigate quantitatively the role of physiologic cyclic mechanical stretch (10% linear stretch; 0.33 Hz: light exercise conditions) on size-dependent cellular uptake and transepithelial transport of nanoparticles (100 nm) and microparticles (1,000 nm) for alveolar epithelial cells (A549) under ALI conditions. Our results show that physiologic stretch enhances cellular uptake of 100 nm nanoparticles across the epithelial cell barrier, but the barrier becomes permeable for both nano- and micron-sized particles (100 and 1,000 nm). This suggests that currently used static in vitro assays may underestimate cellular uptake and transbarrier transport of nanoparticles in the lung